Imaging lens, and electronic apparatus including the same

ABSTRACT

An imaging lens includes first to fifth lens elements arranged from an object side to an image side in the given order. Through designs of surfaces of the lens elements and relevant lens parameters, a short system length of the imaging lens may be achieved while maintaining good optical performance.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Application No.201410085092.8, filed on Mar. 10, 2014.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging lens and an electronicapparatus including the same.

2. Description of the Related Art

In recent years, as use of portable electronic devices (e.g., mobilephones and digital cameras) becomes ubiquitous, much effort has been putinto reducing dimensions of portable electronic devices. Moreover, asdimensions of charged coupled device (CCD) and complementary metal-oxidesemiconductor (CMOS) based optical sensors are reduced, dimensions ofimaging lenses for use with the optical sensors must be correspondinglyreduced without significantly compromising optical performance.

However, the conventional imaging lens with four lens elements isinsufficient to satisfy consumer expectations of high image quality. Itis desirable to develop an imaging lens that has a relatively small sizeand relatively high image quality.

Each of U.S. Pat. Nos. 7,480,105, 7,639,432, 7,486,449 and 7,684,127discloses a type of an imaging lens that includes five lens elements. Ineach of U.S. Pat. Nos. 7,480,105 and 7,639,432, the first two lenselements of the imaging lens disclosed therein respectively have anegative refractive power and a positive refractive power. In each ofU.S. Pat. Nos. 7,486,449 and 7,684,127, both of the first two lenselements of the imaging lens disclosed therein have a negativerefractive power. However, the aforesaid arrangement of the first twolens elements is unable to achieve good optical performance. Beside, theimaging lenses disclosed in the aforesaid patents have a system lengthranging between 10 mm and 18 mm, which disfavors reducing thickness ofportable electronic devices.

Reducing the system length of the imaging lens while maintainingsatisfactory optical performance is always a goal in the industry.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an imaginglens having a shorter overall length while maintaining good opticalperformance.

According to one aspect of the present invention, an imaging lenscomprises an aperture stop, a first lens element, a second lens element,a third lens element, a fourth lens element and a fifth lens elementarranged in order from an object side to an image side along an opticalaxis of the imaging lens. Each of the first lens element, the secondlens element, the third lens element, the fourth lens element and thefifth lens element has a refractive power, an object-side surface facingtoward the object side, and an image-side surface facing toward theimage side.

The first lens element has a positive refractive power, and theobject-side surface of the first lens element is a convex surface thathas a convex portion in a vicinity of the optical axis and a convexportion in a vicinity of a periphery of the first lens element.

The second lens element has a negative refractive power, and theobject-side surface of the second lens element has a concave portion ina vicinity of a periphery of the second lens element.

The image-side surface of the third lens element has a concave portionin a vicinity of the optical axis.

The object-side surface of the fourth lens element has a concave portionin a vicinity of a periphery of the fourth lens element, and theimage-side surface of the fourth lens element has a convex portion in avicinity of the optical axis.

The object-side surface of the fifth lens element has a convex portionin a vicinity of the optical axis, and the image-side surface of thefifth lens element has a concave portion in a vicinity of the opticalaxis, and a convex portion in a vicinity of a periphery of the fifthlens element.

The imaging lens does not include any lens element with a refractivepower other than the first lens element, the second lens element, thethird lens element, the fourth lens element and the fifth lens element.

The imaging lens satisfies T4/G34≧1.60, where T4 represents a thicknessof the fourth lens element at the optical axis, and G34 represents anair gap width between the third lens element and the fourth lens elementat the optical axis.

Another object of the present invention is to provide an electronicapparatus having an imaging lens with five lens elements.

According to another aspect of the present invention, an electronicapparatus includes a housing and an imaging module. The imaging moduleis disposed in the housing, and includes the imaging lens of the presentinvention, a barrel on which the imaging lens is disposed, a holder uniton which the barrel is disposed, and an image sensor disposed at theimage side of the imaging lens.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will becomeapparent in the following detailed description of the preferredembodiments with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram to illustrate the structure of a lenselement;

FIG. 2 is a schematic diagram that illustrates the first preferredembodiment of an imaging lens according to the present invention;

FIG. 3 shows values of some optical data corresponding to the imaginglens of the first preferred embodiment;

FIG. 4 shows values of some aspherical coefficients corresponding to theimaging lens of the first preferred embodiment;

FIGS. 5(a) to 5(d) show different optical characteristics of the imaginglens of the first preferred embodiment;

FIG. 6 is a schematic diagram that illustrates the second preferredembodiment of an imaging lens according to the present invention;

FIG. 7 shows values of some optical data corresponding to the imaginglens of the second preferred embodiment;

FIG. 8 shows values of some aspherical coefficients corresponding to theimaging lens of the second preferred embodiment;

FIGS. 9(a) to 9(d) show different optical characteristics of the imaginglens of the second preferred embodiment;

FIG. 10 is a schematic diagram that illustrates the third preferredembodiment of an imaging lens according to the present invention;

FIG. 11 shows values of some optical data corresponding to the imaginglens of the third preferred embodiment;

FIG. 12 shows values of some aspherical coefficients corresponding tothe imaging lens of the third preferred embodiment;

FIGS. 13(a) to 13(d) show different optical characteristics of theimaging lens of the third preferred embodiment;

FIG. 14 is a schematic diagram that illustrates the fourth preferredembodiment of an imaging lens according to the present invention;

FIG. 15 shows values of some optical data corresponding to the imaginglens of the fourth preferred embodiment;

FIG. 16 shows values of some aspherical coefficients corresponding tothe imaging lens of the fourth preferred embodiment;

FIGS. 17(a) to 17(d) show different optical characteristics of theimaging lens of the fourth preferred embodiment;

FIG. 18 is a schematic diagram that illustrates the fifth preferredembodiment of an imaging lens according to the present invention;

FIG. 19 shows values of some optical data corresponding to the imaginglens of the fifth preferred embodiment;

FIG. 20 shows values of some aspherical coefficients corresponding tothe imaging lens of the fifth preferred embodiment;

FIGS. 21(a) to 21(d) show different optical characteristics of theimaging lens of the fifth preferred embodiment;

FIG. 22 is a schematic diagram that illustrates the sixth preferredembodiment of an imaging lens according to the present invention;

FIG. 23 shows values of some optical data corresponding to the imaginglens of the sixth preferred embodiment;

FIG. 24 shows values of some aspherical coefficients corresponding tothe imaging lens of the sixth preferred embodiment;

FIGS. 25(a) to 25(d) show different optical characteristics of theimaging lens of the sixth preferred embodiment;

FIG. 26 is a schematic diagram that illustrates the seventh preferredembodiment of an imaging lens according to the present invention;

FIG. 27 shows values of some optical data corresponding to the imaginglens of the seventh preferred embodiment;

FIG. 28 shows values of some aspherical coefficients corresponding tothe imaging lens of the seventh preferred embodiment;

FIGS. 29(a) to 29(d) show different optical characteristics of theimaging lens of the seventh preferred embodiment;

FIG. 30 is a table that lists values of relationships among some lensparameters corresponding to the imaging lenses of the first to seventhpreferred embodiments;

FIG. 31 is a schematic partly sectional view to illustrate a firstexemplary application of the imaging lens of the present invention; and

FIG. 32 is a schematic partly sectional view to illustrate a secondexemplary application of the imaging lens of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the present invention is described in greater detail, it shouldbe noted that like elements are denoted by the same reference numeralsthroughout the disclosure.

In the following description, “a lens element has a positive (ornegative) refractive power” means the lens element has a positive (ornegative) refractive power in a vicinity of an optical axis thereof. “Anobject-side surface (or image-side surface) has a convex (or concave)portion at a certain area” means that, compared to a radially exteriorarea adjacent to said certain area, said certain area is more convex (orconcave) in a direction parallel to the optical axis. Referring to FIG.1 as an example, the lens element is radially symmetrical with respectto an optical axis (I) thereof. The object-side surface of the lenselement has a convex portion at an area A, a concave portion at an areaB, and a convex portion at an area C. This is because the area A is moreconvex in a direction parallel to the optical axis (I) in comparisonwith a radially exterior area thereof (i.e., area B), the area B is moreconcave in comparison with the area C, and the area C is more convex incomparison with an area E. “In a vicinity of a periphery” refers to anarea around a periphery of a curved surface of the lens element forpassage of imaging light only, which is the area C in FIG. 1. Theimaging light includes a chief ray Lc and a marginal ray Lm. “In avicinity of the optical axis” refers to an area around the optical axisof the curved surface for passage of the imaging light only, which isthe area A in FIG. 1. In addition, the lens element further includes anextending portion E for installation into an optical imaging lensdevice. Ideally, the imaging light does not pass through the extendingportion E. The structure and shape of the extending portion E are notlimited herein. In the following embodiments, the extending portion E isnot depicted in the drawings for the sake of clarity.

Referring to FIG. 2, the first preferred embodiment of an imaging lens10 according to the present invention includes an aperture stop 2, afirst lens element 3, a second lens element 4, a third lens element 5, afourth lens element 6, a fifth lens element 7, and an optical filter 8arranged in the given order along an optical axis (I) from an objectside to an image side. The optical filter 8 is an infrared cut filterfor selectively absorbing infrared light to thereby reduce imperfectionof images formed at an image plane 100.

Each of the first, second, third, fourth and fifth lens elements 3-7 andthe optical filter 8 has an object-side surface 31, 41, 51, 61, 71, 81facing toward the object side, and an image-side surface 32, 42, 52, 62,72, 82 facing toward the image side. Light entering the imaging lens 10travels through the aperture stop 2, the object-side and image-sidesurfaces 31, 32 of the first lens element 3, the object-side andimage-side surfaces 41, 42 of the second lens element 4, the object-sideand image-side surfaces 51, 52 of the third lens element 5, theobject-side and image-side surfaces 61, 62 of the fourth lens element 6,the object-side and image-side surfaces 71, 72 of the fifth lens element7, and the object-side and image-side surfaces 81, 82 of the opticalfilter 8, in the given order, to form an image on the image plane 100.Each of the object-side surfaces 31, 41, 51, 61, 71 and the image-sidesurfaces 32, 42, 52, 62, 72 is aspherical and has a center pointcoinciding with the optical axis (I).

Each of the lens elements 3-7 is made of a plastic material and has arefractive power in this embodiment. However, at least one of the lenselements 3-7 may be made of other materials in other embodiments.

In the first preferred embodiment, which is depicted in FIG. 2, thefirst lens element 3 has a positive refractive power. The object-sidesurface 31 of the first lens element 3 is a convex surface that has aconvex portion 311 in a vicinity of the optical axis (I) and that has aconvex portion 312 in a vicinity of a periphery of the first lenselement 3. The image-side surface 32 of the first lens element 3 has aconcave portion 321 in a vicinity of the optical axis (I), and a convexportion 322 in a vicinity of the periphery of the first lens element 3.

The second lens element 4 has a negative refractive power. Theobject-side surface 41 of the second lens element 4 has a convex portion411 in a vicinity of the optical axis (I), and a concave portion 412 ina vicinity of a periphery of the second lens element 4. The image-sidesurface 42 of the second lens element 4 has a concave portion 421 in avicinity of the optical axis (I), and a convex portion 422 in a vicinityof the periphery of the second lens element 4.

The third lens element 5 has a positive refractive power. Theobject-side surface 51 of the third lens element 5 has a convex portion511 in a vicinity of the optical axis (I), and a concave portion 512 ina vicinity of a periphery of the third lens element 5. The image-sidesurface 52 of the third lens element 5 has a concave portion 521 in avicinity of the optical axis (I), and a convex portion 522 in a vicinityof the periphery of the third lens element 5.

The fourth lens element 6 has a positive refractive power. Theobject-side surface 61 of the fourth lens element 6 is a concave surfacethat has a concave portion 611 in a vicinity of the optical axis (I),and a concave portion 612 in a vicinity of a periphery of the fourthlens element 6. The image-side surface 62 of the fourth lens element 6is a convex surface that has a convex portion 621 in a vicinity of theoptical axis (I), and a convex portion 622 in a vicinity of theperiphery of the fourth lens element 6.

The fifth lens element 7 has a negative refractive power. Theobject-side surface 71 of the fifth lens element 7 has a convex portion711 in a vicinity of the optical axis (I), and a concave portion 712 ina vicinity of a periphery of the fifth lens element 7. The image-sidesurface 72 of the fifth lens element 7 has a concave portion 721 in avicinity of the optical axis (I), and a convex portion 722 in a vicinityof the periphery of the fifth lens element 7.

In the first preferred embodiment, the imaging lens 10 does not includeany lens element with a refractive power other than the aforesaid lenselements 3-7.

Shown in FIG. 3 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the first preferredembodiment. The imaging lens 10 has an overall system effective focallength (EFL) of 2.6385 mm, a half field-of-view (HFOV) of 40.425°, anF-number of 2.05, and a system length of 3.9041 mm. The system lengthrefers to a distance between the object-side surface 31 of the firstlens element 3 and the image plane 100 at the optical axis (I).

In this embodiment, each of the object-side surfaces 31-71 and theimage-side surfaces 32-72 is aspherical, and satisfies the relationshipof

$\begin{matrix}{{Z(Y)} = {{\frac{Y^{2}}{R}/\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}{a_{2\; i} \times Y^{2\; i}}}}} & (1)\end{matrix}$

where:

R represents a radius of curvature of an aspherical surface;

Z represents a depth of the aspherical surface, which is defined as aperpendicular distance between an arbitrary point on the asphericalsurface that is spaced apart from the optical axis (I) by a distance Y,and a tangent plane at a vertex of the aspherical surface at the opticalaxis (I);

Y represents a perpendicular distance between the arbitrary point on theaspherical surface and the optical axis (I);

K represents a conic constant; and

a_(2i) represents a 2i^(th) aspherical coefficient.

Shown in FIG. 4 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thefirst preferred embodiment.

Relationships among some of the lens parameters corresponding to thefirst preferred embodiment are listed in a column of FIG. 30corresponding to the first preferred embodiment, where:

T1 represents a thickness of the first lens element 3 at the opticalaxis (I);

T2 represents a thickness of the second lens element 4 at the opticalaxis (I);

T3 represents a thickness of the third lens element 5 at the opticalaxis (I);

T4 represents a thickness of the fourth lens element 6 at the opticalaxis (I);

T5 represents a thickness of the fifth lens element 7 at the opticalaxis (I);

G12 represents an air gap width between the first lens element 3 and thesecond lens element 4 at the optical axis (I);

G23 represents an air gap width between the second lens element 4 andthe third lens element 5 at the optical axis (I);

G34 represents an air gap width between the third lens element 5 and thefourth lens element 6 at the optical axis (I);

G45 represents an air gap′width between the fourth lens element 6 andthe fifth lens element 7 at the optical axis (I);

ALT represents a sum of thicknesses of the lens elements 3-7 at theoptical axis (I), i.e., the sum of T1, T2, T3, T4, and T5;

Gaa represents a sum of four air gap widths among the first lens element3, the second lens element 4, the third lens element 5, the fourth lenselement 6 and the fifth lens element 7 at the optical axis (I), i.e.,the sum of G12, G23, G34, and G45; and

BFL represents a distance at the optical axis (I) between the image-sidesurface 72 of the fifth lens element 7 and the image plane 100 at theimage side.

FIGS. 5(a) to 5(d) respectively show simulation results corresponding tolongitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thefirst preferred embodiment. In each of the simulation results, curvescorresponding respectively to wavelengths of 470 nm, 555 nm, and 650 nmare shown.

It can be understood from FIG. 5(a) that, since each of the curvescorresponding to longitudinal spherical aberration has a focal length ateach field of view (indicated by the vertical axis) that falls withinthe range of ±0.02 mm, the first preferred embodiment is able to achievea relatively low spherical aberration at each of the wavelengths.Furthermore, since the curves at each field of view are close to eachother, the first preferred embodiment has a relatively low chromaticaberration.

It can be understood from FIGS. 5(b) and 5(c) that, since each of thecurves falls within the range of ±0.2 mm of focal length, the firstpreferred embodiment has a relatively low optical aberration.

Moreover, as shown in FIG. 5(d), since each of the curves correspondingto distortion aberration falls within the range of ±1%, the firstpreferred embodiment is able to meet requirements in imaging quality ofmost optical systems.

In view of the above, even with the system length reduced down to below4.00 mm, the imaging lens 10 of the first preferred embodiment is stillable to achieve a relatively good optical performance.

Referring to FIG. 6, the differences between the first and secondpreferred embodiments of the imaging lens 10 of this invention reside insome of the optical data corresponding to the surfaces 31-81, 32-82, thelens parameters and the aspherical coefficients of the lens elements3-7.

Shown in FIG. 7 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the second preferredembodiment. The imaging lens 10 has an overall system focal length of2.6174 mm, an HFOV of 40.650°, an F-number of 2.05, and a system lengthof 3.8859 mm.

Shown in FIG. 8 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thesecond preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the second preferred embodiment are listed in a columnof FIG. 30 corresponding to the second preferred embodiment.

FIGS. 9(a) to 9(d) respectively show simulation results corresponding tolongitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thesecond preferred embodiment. It can be understood from FIGS. 9(a) to9(d) that the second preferred embodiment is able to achieve arelatively good optical performance.

Referring to FIG. 10, the differences between the first and thirdpreferred embodiments of the imaging lens 10 of this invention reside insome of the optical data corresponding to the surfaces 31-81, 32-82, thelens parameters, and the aspherical coefficients of the lens elements3-7.

Shown in FIG. 11 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the third preferredembodiment. The imaging lens 10 has an overall system focal length of2.7389 mm, an HFOV of 39.421°, an F-number of 2.05, and a system lengthof 4.1354 mm.

Shown in FIG. 12 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thethird preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the third preferred embodiment are listed in a columnof FIG. 30 corresponding to the third preferred embodiment.

FIGS. 13(a) to 13(d) respectively show simulation results correspondingto longitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thethird preferred embodiment. It can be understood from FIGS. 13(a) to13(d) that the third preferred embodiment is able to achieve arelatively good optical performance.

Referring to FIG. 14, the differences between the first and fourthpreferred embodiments of the imaging lens 10 of this invention reside insome of the optical data corresponding to the surfaces 31-81, 32-82, thelens parameters, and the aspherical coefficients of the lens elements3-7.

Shown in FIG. 15 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the fourth preferredembodiment. The imaging lens 10 has an overall system focal length of2.7359 mm, an HFOV of 39.385°, an F-number of 2.05, and a system lengthof 4.0700 mm.

Shown in FIG. 16 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thefourth preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the fourth preferred embodiment are listed in a columnof FIG. 30 corresponding to the fourth preferred embodiment.

FIGS. 17(a) to 17(d) respectively show simulation results correspondingto longitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thefourth preferred embodiment. It can be understood from FIGS. 17(a) to17(d) that the fourth preferred embodiment is able to achieve arelatively good optical performance.

Referring to FIG. 18, the differences between the first and fifthpreferred embodiments of the imaging lens 10 of this invention reside insome of the optical data corresponding to the surfaces 31-81, 32-82, thelens parameters, and the aspherical coefficients of the lens elements3-7. Besides, in the fifth preferred embodiment, the image-side surface62 of the fourth lens element 6 has a convex portion 621 in a vicinityof the optical axis (I), and a concave portion 623 in a vicinity of aperiphery of the fourth lens element 6.

Shown in FIG. 19 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the fifth preferredembodiment. The imaging lens 10 has an overall system focal length of2.6899 mm, an HFOV of 39.812°, an F-number of 2.05, and a system lengthof 3.9004 mm.

Shown in FIG. 20 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thefifth preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the fifth preferred embodiment are listed in a columnof FIG. 30 corresponding to the fifth preferred embodiment.

FIGS. 21(a) to 21(d) respectively show simulation results correspondingto longitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thefifth preferred embodiment. It can be understood from FIGS. 21(a) to21(d) that the fifth preferred embodiment is able to achieve arelatively good optical performance.

Referring to FIG. 22, the differences between the first and sixthpreferred embodiments of the imaging lens 10 of this invention reside insome of the optical data corresponding to the surfaces 31-81, 32-82, thelens parameters, and the aspherical coefficients of the lens elements3-7.

Shown in FIG. 23 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the sixth preferredembodiment. The imaging lens 10 has an overall system focal length of2.7384 mm, an HFOV of 39.418°, an F-number of 2.05, and a system lengthof 4.1644 mm.

Shown in FIG. 24 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to thesixth preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the sixth preferred embodiment are listed in a columnof FIG. 30 corresponding to the sixth preferred embodiment.

FIGS. 25(a) to 25(d) respectively show simulation results correspondingto longitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of thesixth preferred embodiment. It can be understood from FIGS. 25(a) to25(d) that the sixth preferred embodiment is able to achieve arelatively good optical performance.

FIG. 26 illustrates the seventh preferred embodiment of an imaging lens10 according to the present invention, which has a configuration similarto that of the first preferred embodiment. However, in this seventhpreferred embodiment, the image-side surface 42 of the second lenselement 4 has a concave portion 421 in a vicinity of the optical axis(I), and a concave portion 423 in a vicinity of a periphery of thesecond lens element 4.

Shown in FIG. 27 is a table that lists values of some optical datacorresponding to the surfaces 31-81, 32-82 of the seventh preferredembodiment. The imaging lens 10 has an overall system focal length of2.5570 mm, an HFOV of 41.121°, an F-number of 2.05, and a system lengthof 3.8139 mm.

Shown in FIG. 28 is a table that lists values of some asphericalcoefficients of the aforementioned relationship (1) corresponding to theseventh preferred embodiment.

Relationships among some of the aforementioned lens parameterscorresponding to the seventh preferred embodiment are listed in a columnof FIG. 30 corresponding to the seventh preferred embodiment.

FIGS. 29(a) to 29(d) respectively show simulation results correspondingto longitudinal spherical aberration, sagittal astigmatism aberration,tangential astigmatism aberration, and distortion aberration of theseventh preferred embodiment. It can be understood from FIGS. 29(a) to29(d) that the seventh preferred embodiment is able to achieve arelatively good optical performance.

Shown in FIG. 30 is a table that lists the aforesaid relationships amongsome of the aforementioned lens parameters corresponding to the sevenpreferred embodiments for comparison. It should be noted that the valuesof the lens parameters and the relationships listed in FIG. 30 arerounded off to the third decimal place.

When each of the lens parameters of the imaging lens 10 according tothis invention satisfies the following optical relationships, theoptical performance is still relatively good even with the reducedsystem length:

1. T4/G34≧1.60 and T3/G34≧1.10: In order to reduce the overall systemlength of the imaging lens 10, reductions in T3, T4 and G34 areadvantageous. However, although G34 is readily reduced, reductions in T3and T4 are limited due to manufacturing ability. In design, there is atendency to have relatively larger values of T4/G34 and T3/G34. Betterarrangement may be achieved when these relationships are satisfied.Preferably, 1.6≦T4/G34≦5.0 and 1.1≦T3/G34≦2.5.

2. T3/G23≧1.80, T2/G23≧1.20, T1/G23≧2.80, T4/G23≧3.00, T5/G23≧2.55 andALT/G23≧11.00: Similar to the above, reductions in T1, T2, T3, T4, T5and ALT are limited, while G23 should be reduced as much as possible forreduction of the overall system length of the imaging lens 10.Therefore, there is a tendency to have relatively larger values ofT3/G23, T2/G23, T1/G23, T4/G23, T5/G23 and ALT/G23 in design. Betterarrangement may be achieved when these relationships are satisfied.Preferably, 1.8≦T3/G23≦9.0, 1.2≦T2/G23≦5.0, 2.8≦T1/G23≦10.0,2.55≦T5/G23≦12.0, 3.0T4/G23≦12.0 and 11.0≦ALT/G23≦50.0.

3. T1/Gaa≧0.65 and Gaa/T2≦3.00: Similar to the above aforesaid, Gaashould be reduced as much as possible for reduction of the overallsystem length of the imaging lens 10. Therefore, T1/Gaa tends to have arelatively larger value, and Gaa/T2 tends to have a relatively smallervalue in design. Better arrangement may be achieved when theserelationships are satisfied. Preferably, 0.65≦T1/Gaa≦1.1 and1.8≦Gaa/T2≦3.0.

4. T5/T4≧0.70, ALT/T1≦5.00 and BFL/T5≦3.00: In order to prevent any oneof the lens elements 3-7 from being too thick that disfavors reductionof the overall system length, and from being too thin that disfavorslens manufacture, T5/T4, ALT/T1 and BFL/T5 should be maintained atappropriate relationships, respectively. Better arrangement may beachieved when these relationships are satisfied. Preferably,0.7≦T5/T4≦1.2, 4.0≦ALT/T1≦5.0 and 1.5≦BFL/T5≦3.0.

5. BFL/(G12+G45)≧3.00, (G12+G45)/G23≦4.00 and Gaa/(G12+G45)≧2.50: Sincethe image-side surface 62 of the fourth lens element 6 has the convexportion 621 in the vicinity of the optical axis (I) and the object-sidesurface 71 of the fifth lens element 7 has the convex portion 711 in thevicinity of the optical axis (I), G45 can be reduced as much as possiblein comparison with other air gap widths. In design, BFL/(G12+G45) andGaa/(G12+G45) tend to have relatively larger values, and (G12+G45)/G23tends to have a relatively smaller value. Better arrangement may beachieved when these relationships are satisfied. Preferably,3.0≦BFL/(G12+G45)≦10.0, 0.5≦(G12+G45)/G23≦4.0 and 2.5≦Gaa/(G12+G45)≦5.0.

To sum up, effects and advantages of the imaging lens 10 according tothe present invention are described hereinafter.

1. The positive refractive power of the first lens element 3 contributesto the overall positive refractive power of the imaging lens 10. Thenegative refractive power of the second lens element 2 is effective tocorrect image aberration. In addition, by virtue of the aperture stop 2arranged in front of the object-side surface 31 of the first lenselement 3, converging ability may be enhanced, and the overall length ofthe imaging lens 10 may be reduced.

2. Through design of the relevant optical parameters, opticalaberrations, such as spherical aberration, may be reduced or eveneliminated. Moreover, by cooperation of the convex object-side surface31 that favors collecting imaging lights, the concave portion 412, theconcave portion 521, the concave portion 611, the convex portion 621,the convex portion 711, the concave portion 721 and the convex portion722, image quality may be enhanced.

3. Through the aforesaid seven preferred embodiments, it is known thatthe system length of this invention may be reduced down to below 4.2 mm,so as to facilitate developing thinner relevant products with economicbenefits.

Shown in FIG. 31 is a first exemplary application of the imaging lens10, in which the imaging lens 10 is disposed in a housing 11 of anelectronic apparatus 1 (such as a mobile phone, but not limitedthereto), and forms a part of an imaging module 12 of the electronicapparatus 1.

The imaging module 12 includes a barrel 21 on which the imaging lens 10is disposed, a holder unit 120 on which the barrel 21 is disposed, andan image sensor 130 disposed at the image plane 100 (see FIG. 2).

The holder unit 120 includes a first holder portion 121 in which thebarrel 21 is disposed, and a second holder portion 122 having a portioninterposed between the first holder portion 121 and the image sensor130. The barrel 21 and the first holder portion 121 of the holder unit120 extend along an axis (II), which coincides with the optical axis (I)of the imaging lens 10.

Shown in FIG. 32 is a second exemplary application of the imaging lens10. The differences between the first and second exemplary applicationsreside in that, in the second exemplary application, the holder unit 120is configured as a voice-coil motor (VCM), and the first holder portion121 includes an inner section 123 in which the barrel 21 is disposed, anouter section 124 that surrounds the inner section 123, a coil 125 thatis interposed between the inner and outer sections 123, 124, and amagnetic component 126 that is disposed between an outer side of thecoil 125 and an inner side of the outer section 124.

The inner section 123 and the barrel 21, together with the imaging lens10 therein, are movable with respect to the image sensor 130 along anaxis (III), which coincides with the optical axis (I) of the imaginglens 10. The optical filter 8 of the imaging lens 10 is disposed at thesecond holder portion 122, which is disposed to abut against the outersection 124. Configuration and arrangement of other components of theelectronic apparatus 1 in the second exemplary application are identicalto those in the first exemplary application, and hence will not bedescribed hereinafter for the sake of brevity.

By virtue of the imaging lens 10 of the present invention, theelectronic apparatus 1 in each of the exemplary applications may beconfigured to have a relatively reduced overall thickness with goodoptical and imaging performance, so as to reduce cost of materials, andsatisfy requirements of product miniaturization.

While the present invention has been described in connection with whatare considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements includedwithin the spirit and scope of the broadest interpretation so as toencompass all such modifications and equivalent arrangements.

What is claimed is:
 1. An imaging lens comprising an aperture stop, afirst lens element, a second lens element, a third lens element, afourth lens element and a fifth lens element arranged in order from anobject side to an image side along an optical axis of said imaging lens,each of said first lens element, said second lens element, said thirdlens element, said fourth lens element and said fifth lens elementhaving a refractive power, an object-side surface facing toward theobject side, and an image-side surface facing toward the image side,wherein: said first lens element has a positive refractive power, andsaid object-side surface of said first lens element is a convex surfacethat has a convex portion in a vicinity of the optical axis and a convexportion in a vicinity of a periphery of said first lens element; saidsecond lens element has a negative refractive power, and saidobject-side surface of said second lens element has a concave portion ina vicinity of a periphery of said second lens element; said image-sidesurface of said third lens element has a concave portion in a vicinityof the optical axis; said object-side surface of said fourth lenselement has a concave portion in a vicinity of a periphery of saidfourth lens element, said fourth lens element has a positive refractivepower, and said image-side surface of said fourth lens element has aconvex portion in a vicinity of the optical axis; said object-sidesurface of said fifth lens element has a convex portion in a vicinity ofthe optical axis, and said image-side surface of said fifth lens elementhas a concave portion in a vicinity of the optical axis, and a convexportion in a vicinity of a periphery of said fifth lens element; saidimaging lens does not include any lens element with a refractive powerother than said first lens element, said second lens element, said thirdlens element, said fourth lens element and said fifth lens element; saidimaging lens satisfies T4/G34≧1.60, where T4 represents a thickness ofsaid fourth lens element at the optical axis, and G34 represents an airgap width between said third lens element and said fourth lens elementat the optical axis; and said imaging lens further satisfiesT4/G23≧3.00, where G23 represents an air gap width between said secondlens element and said third lens element at the optical axis.
 2. Theimaging lens as claimed in claim 1, further satisfying T5/T4≧0.70, whereT5 represents a thickness of said fifth lens element at the opticalaxis.
 3. The imaging lens as claimed in claim 2, further satisfyingT3/G23≧1.80, where T3 represents a thickness of said third lens elementat the optical axis.
 4. The imaging lens as claimed in claim 3, furthersatisfying T1/Gaa≧0.65, where T1 represents a thickness of said firstlens element at the optical axis, and Gaa represents a sum of four airgap widths among said first lens element, said second lens element, saidthird lens element, said fourth lens element and said fifth lens elementat the optical axis.
 5. The imaging lens as claimed in claim 3, furthersatisfying T2/G23≧1.20, where T2 represents a thickness of said secondlens element at the optical axis.
 6. The imaging lens as claimed inclaim 5, further satisfying ALT/T1≦5.00, where T1 represents a thicknessof said first lens element at the optical axis, and ALT represents a sumof thicknesses of said first lens element, said second lens element,said third lens element, said fourth lens element and said fifth lenselement at the optical axis.
 7. The imaging lens as claimed in claim 1,further satisfying BFL/(G12+G45)≧3.00, where BFL represents a distanceat the optical axis between said image-side surface of said fifth lenselement and an image plane at the image side, G12 represents an air gapwidth between said first lens element and said second lens element atthe optical axis, and G45 represents an air gap width between saidfourth lens element and said fifth lens element at the optical axis. 8.The imaging lens as claimed in claim 7, further satisfying T3/G34≧1.10,where T3 represents a thickness of said third lens element at theoptical axis.
 9. The imaging lens as claimed in claim 8, furthersatisfying T1/G23≧2.80, where T1 represents a thickness of said firstlens element at the optical axis.
 10. The imaging lens as claimed inclaim 9, further satisfying (G12+G45)/G23≧4.00.
 11. The imaging lens asclaimed in claim 9, further satisfying BFL/T5≦3.00, where T5 representsa thickness of said fifth lens element at the optical axis.
 12. Theimaging lens as claimed in claim 1, further satisfying T3/G23≧1.80,where T3 represents a thickness of said third lens element at theoptical axis.
 13. The imaging lens as claimed in claim 12, furthersatisfying Gaa/(G12+G45)≧2.50, where Gaa represents a sum of four airgap widths among said first lens element, said second lens element, saidthird lens element, said fourth lens element and said fifth lens elementat the optical axis, G12 represents the air gap width between said firstlens element and said second lens element at the optical axis, and G45represents the air gap width between said fourth lens element and saidfifth lens element at the optical axis.
 14. The imaging lens as claimedin claim 13, further satisfying T5/G23≧2.55, where T5 represents athickness of said fifth lens element at the optical axis.
 15. Theimaging lens as claimed in claim 13, further satisfying Gaa/T2≦3.00,where T2 represents a thickness of said second lens element at theoptical axis.
 16. The imaging lens as claimed in claim 1, furthersatisfying T3/G34≧1.10, where T3 represents a thickness of said thirdlens element at the optical axis.
 17. The imaging lens as claimed inclaim 16, further satisfying T5/T4≧0.70, where T5 represents a thicknessof said fifth lens element at the optical axis.
 18. The imaging lens asclaimed in claim 17, further satisfying ALT/G23≧11.00, where ALTrepresents a sum of thicknesses of said first lens element, said secondlens element, said third lens element, said fourth lens element and saidfifth lens element at the optical axis.
 19. An electronic apparatuscomprising: a housing; and an imaging module disposed in said housing,and including an imaging lens as claimed in claim 1, a barrel on whichsaid imaging lens is disposed, a holder unit on which said barrel isdisposed, and an image sensor disposed at the image side of said imaginglens.